1. Field of the Invention
The present disclosure generally relates to a semiconductor memory device, and more particularly, to a flash memory device.
2. Description of the Related Art
Semiconductor memory devices are widely used to store data. Specifically, semiconductor memory devices are used in a wide variety of electronic equipment. The electronic equipment may range from satellite equipment to consumer electronic equipment. With the increasing demand for high speed but yet small size electronic equipment, there is an increasing demand for semiconductor memory devices that operate at higher speeds than before but are smaller in size.
The semiconductor memory devices are largely divided into volatile memory devices and non-volatile memory devices. Many differences exist between volatile memory devices and non-volatile memory devices. For example, volatile memory devices loose stored data in the event of power loss. However, non-volatile memory devices tend to retain stored data even in the event of a power loss.
Non-volatile memory devices include, for example, Magnetic Read Only Memory (MROM), Programmable Read Only Memory (PROM), Electrically Programmable Read Only Memory (EPROM), and Electrically Erasable Programmable Read Only Memory (EEPROM). An MROM, PROM, and EPROM may not easily erase and write data stored therein. This difficulty in writing data to and erasing data from these memory devices may make it difficult for non-sophisticated users to use these kinds of memory devices. On the other hand, EEPROM may electrically erase and write data such with relative ease. This ease in erasing and writing data has made the EEPROM a popular choice for a non-volatile memory device. In particular, a flash EEPROM (hereinafter, referred to as a flash memory) has a higher degree of integration compared to conventional EEPROM. Different types of flash memories are commercially available at this time. These types include, for example, a NAND flash memory and a NOR flash memory. NAND flash memories and NOR flash memories have different characteristics. For example, a NAND flash memory has a higher degree of integration than a NOR flash memory.
Generally, a NOR flash memory is used for storing codes and program data. Furthermore, as a device that includes a NOR flash memory requires increasing amounts of code and program data, the programming time for the device increases. This increase in programming time is generally due to the time taken in providing the data, addresses, and commands required for each programming operation to the device via the NOR flash memory. However, the programming time in this situation may be reduced by storing the data, addresses, and commands for each program operation in a buffer of the NOR flash memory. For example, data may be loaded into a buffer of the NOR flash memory, and then the loaded data may be programmed by a simultaneous programming unit (e.g., ×4, ×8, ×16, etc.) without the need to load data for each programming operation one at a time.
One will appreciate that the size of the buffer for temporarily storing the program data increases in proportion to an increase in the size of the code and program data. This means that the layout region of the NOR flash memory increases. There is therefore a need for reducing the size of the buffer in a flash memory device without reducing the amount of data and code that may be stored in the flash memory device.